This invention is directed to resinous rods reinforced with longitudinal graphite or silicon carbide fibers. More specifically, this invention is directed to tapered resilient flexible hollow fishing rods composed of a heat-curable resin matrix reinforced with unidirectional longitudinally aligned graphite or silicon carbide fibers.
The production of fiber-reinforced hollow rods, such as fishing rods, in recent years has involved wrapping fibers around a mandrel, employing an epoxy or other suitable curable resin as a binder. The fibers and resin may be formed directly onto the mandrel or may be available in the form of a woven or non-woven matrix which is cut to a suitable pattern and wrapped around the mandrel. The rod is then subjected to the required curing, after which the mandrel is removed leaving the hollow fishing rod blank.
In order to achieve specific characteristics in the rods, various types of fibers and various configurations of the fiber plies have been suggested. For example, U.S. Pat. No. 2,749,643 discloses a hollow shaft for fishing rods, having a surface ayer of longitudinally extending glass fibers and an inner layer of circumferentially wound glass fibers. The longitudinal fibers are disclosed to provide tension and compression strength, while the inner circumferentially wound fibers serve to retain the circular profile of the rod and maintain the moment of bending inertia of the shaft.
In the glass fiber reinforced rod of U.S. Pat. No. 3,260,010, two resinous layers, each having longitudinally aligned fibers, are superimposed so that the fibers of one layer form an acute angle with those of the other layer, and this dual layer is then wound about the mandrel to form the rod. This arrangement is said to provide hoop strength to ensure resistance to crushing in the rod, while the generally longitudinal alignment of the fibers is said to support the flexural stresses.
Graphite fibers are used to provide the reinforcement in the tapered hollow fishing rods of U.S. Pat. No. 4,043,074. The inner fiber-reinforced layers have the fibers aligned at an angle of 30 to 45 degrees to the axis of the rod. In the outer layers, the fibers extend generally parallel to the length of the rod. Due to the way in which the plies are rolled onto the tapered mandrel, the exterior fibers at the large diameter end of the rod align themselves at an increasing angle to the axis of the rod. U.S. Pat. No. 4,043,074 recognizes that rods of graphite fiber reinforcement exhibit a tendency to concentrate flexural forces near the large diameter handle end, unless the rod is made larger or heavier. However, U.S. Pat. No. 4,043,074 indicates that their arrangement of multiple layers of differently aligned fibers forms a rod of sufficient flexibility to resist breakage during flexure.
Both graphite and glass fibers have been used together to provide rod reinforcement, as illustrated in U.S. Pat. No. 4,061,806, wherein an inner layer of helically wound graphite fibers and an outer layer of longitudinally extending glass fibers are bonded together with a plastic resin. This arrangement of fibers is said to be required in order to provide both sufficient bending strength and necessary hoop or crushing strength to the rod.